When a conventional physical vapor deposition (PVD) method or a non-thermodynamical equilibrium process, such as a sputtering method or a pulsed laser deposition (PLD) method is used to prepare a multicomponent oxide thin film, undesirable defects or precipitations are inevitably introduced in the inside of the thin film. Such defects or precipitations will present a serious hazard to developments of high-temperature superconducting devices such as superconducting tunnel junction devices or microwave devices.
In order to solve this problem, the inventors proposed a new method of growing an epitaxial thin film under three phases: solid phase (a seed layer), liquid phase (liquid layer on the seed layer) and gas phase (gas serving as deposition seed), or a tri-phase epitaxy (TPE) method, and reported that a Nd1+xBa2−xCu3O7−y thin film could be fabricated substantially in the form of a single crystal through the tri-phase epitaxy method (“Tri-phase epitaxy for single crystalline superconducting thin films” The Third Symposium on Atomic-scale Surface and Interface Dynamics, 4-5 Mar., 1999).